Lighting design of high quality biomedical devices

ABSTRACT

The invention relates to a plurality of light sources to power a variety of applications including microarray readers, microplate scanners, microfluidic analyzers, sensors, sequencers, Q-PCR and a host of other bioanalytical tools that drive today&#39;s commercial, academic and clinical biotech labs.

CLAIM OF PRIORITY

This present application is a continuation application U.S. patentapplication Ser. No. 13/484,031, filed May 30, 2012, entitled “LightingDesign of High Quality Biomedical Devices” which is a continuationapplication of and claims priority to U.S. patent application Ser. No.12/691,601, filed Jan. 21, 2010, now U.S. Pat. No. 8,242,462, issuedAug. 14, 2012, entitled “Lighting Design of High Quality BiomedicalDevices” which claims the benefit of priority under 35 U.S.C. §119(e) toU.S. Provisional Patent Application No. 61/147,040, filed on Jan. 23,2009, entitled “Lighting Design of High Quality Biomedical Devices,” allor which applications are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to using Light Emitting Diodes forillumination.

BACKGROUND OF THE INVENTION

Among the trends redefining 21st century biomedical diagnostics andtherapeutics is the design of low-cost portable analyzers. Because lightis a powerful tool in many of today's most widely used life scienceinstruments, high intensity, low cost light engines are essential to thedesign and proliferation of the newest bio-analytical instruments,medical devices and miniaturized analyzers. The development of new lighttechnology represents a critical technical hurdle in the realization ofpoint-of-care analysis.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to methods and devicesfor converting the output of a specific color LED and generating abroader band of wavelengths of emission including not only the specificcolor but additional color output. Specific embodiments, as will bedescribed below, minimize backward directed light while increasing thetotal range of wavelengths emitted.

Lighting for life sciences is a broad and general category. Not only arethe source specifications varied but so too are the equally importantoptical delivery requirements. Spectral and spatial lightingrequirements for sensing on the head of an optical probe or within asingle cell in a flowing stream differ in output power by orders ofmagnitude from the requirements of a multi-analyte detection scheme onan analysis chip or within the wells of a micro-titer plate. The numberof colors, spectral purity, spectral and power stability, durability andswitching requirements are each unique. Illuminating hundreds ofthousands of spots for quantitative fluorescence within a micro-arraymay be best served by projection optics while microscopes set demandingspecifications for light delivery to overfill the back aperture of themicroscope objective within optical trains specific to each scope bodyand objective design.

While lighting manufacturers cannot provide all things to allapplications, it is precisely this breadth of demand for which a lightengine can be designed. To that end, products are not simple sources,but rather light engines: sources and all the ancillary componentsrequired to provide pure, powerful, light to the sample or as close toit as mechanically possible. Such designs have resulted in products thatembody a flexible, hybrid solution to meet the needs of the broad arrayof applications for biotech. A qualitative comparison of light engineperformance as a function of source technology is summarized in Table 1.

TABLE I A qualitative comparison of light engine performance as functionof the source technology employed Source Useable Temporal HeatTechnology Light Uniformity Response Generation Durability Cost Arc Lampmed poor none high low high Laser high poor none low low very high LEDlow poor fast low high medium Tungsten low poor none medium low mediumLight Pipe high high fast low high low

Historically arc lamps are noted to be flexible sources in that theyprovide white light. The output is managed, with numerous opticalelements, to select for the wavelengths of interest and for typicalfluorescence based instruments, to discriminate against the emissionbands. However their notorious instability and lack of durability inaddition to their significant heat management requirements make themless than ideal for portable analyzers. Moreover, large power demands todrive them present a barrier to battery operation within a compactdesign.

Lasers require a trained user and significant safety precautions. Whilesolid state red outputs are cost effective, the shorter wavelengthoutputs are typically costly, require significant maintenance andancillary components. Color balance and drift for multi-line outputs isa serious complication to quantitative analyses based on lasers.Moreover, the bulk of fluorescence applications do not need coherentlight, are complicated by speckle patterns and do not require suchnarrowband outputs. Overcoming each of these traits requires lightmanagement and adds cost to the implementation of lasers for mostbio-analytical tools.

Finally LEDs, have matured significantly within the last decades. LEDsare now available in a relatively wide range of wavelengths. Howevertheir output is significantly broad so as to require filtering.Additionally, output in the visible spectrum is profoundly reduced inthe green, 500-600 not. The LED also presents trade-offs with respect toemission wavelength dependent intensity, broad emission spectrum(spectral half width on the order of 30 nm or more), poor spectralstability, and the wide angular range of emission. In addition, theprocess used to manufacture LED's cannot tightly control their spectralstability; anyone wishing to use LED's in applications requiring a goodspectral stability must work directly with a supplier to essentiallyhand-pick the LED's for the particular application. Finally, LED'sgenerate light over a wide angular range (50% of light intensity emittedat 70°). While optics can narrow the emission band and focus the lightoutput, the resulting loss in power and increase in thermal outputfurther limit the feasibility of LED light engines.

Most importantly, these light technologies cannot be readily improvedfor bioanalytical applications. The associated light engine marketsimply does not justify the large investment necessary to overcomefundamental performance limitations. As a result, analytical instrumentperformance and price is constrained by the light source with no clearsolution in sight. Moreover the numerous manufacturers of lamps andlasers provide only a source, not an integrated light engine. Companiessuch as ILC Technology, Lumileds, Spectra-Physics, Sylvania and CooILEDrequire some sort of mechanics and or electro-optics such asacousto-optic tunable filters (AOTFs), excitation filters (with a wheelor cube holder), shutters and controllers.

While no one lighting solution can best satisfy all instrumentarchitectures, a light pipe engine combines the best of solid statetechnologies to meet or outperform the traditional technologies listedin Table I on the basis of all figures of merit for all individualwavelengths. Key to this performance is the light pipe architecture.Single outputs, such as red from a diode laser, may be competitive.However, no family of outputs can by assembled that bests the light pipedisclosed herein. In an embodiment of the invention, a light pipe enginecan emit narrowband light exceeding 500 mW/color with intensifies up to10 W/cm² depending on the application. In an embodiment of theinvention, bandwidths as narrow as 10 nm are achievable. While suchoutput power and overall emission intensity is impressive, the mostsignificant figure of merit for quantifying the value of any lightingsubsystem for bio-analytics is the intensity of high qualityillumination provided to the sample. This is a factor dictated by theinstrument design and sample volume and clearly very applicationspecific.

In the case of medical devices and portable diagnostics the presentlight pipe invention offers a smart alternative for light generation.The light pipe engine is an optical subsystem; it consists of lampmodules for each discrete output based on solid state technologiestailored to best satisfy that output requirement complete withcollection and delivery optics. The capabilities of the light pipeengine are highlighted in Table 2. The high performance illuminationprovided by the light pipe engine is embodied in a single compact unitdesigned to replace the entire ensemble of lighting components. Thesources, excitation filters, multicolor switching capabilities and fastpulsing are contained within one box such that no external optics ormechanics are required.

TABLE II Light pipe engine metrics of an embodiment of the invention,designed to meet the needs for portable fluorescence assays andbiomedical devices. Key Metrics: Spectral Output Up to eight colorsspanning UV-Vis-NIR >_ 100 mW/spectral band 1-10 W/cm Peak WavelengthOptimal for different floors, adjustable bandwidths Power Stability >99%over 24 hours Spectral Width 10 to 50 nm Spectral Drift <1% in 24 hoursColor Dependence None Lifetime >5000 hrs Footprint amenable toportability Maintenance None, no replacement components for the lightengines lifetime

An inexpensive lighting solution, uniquely well suited to the productionof safe, effective and commercially viable life science tools andbiomedical devices can be attained using a solid-state light engine. Inan embodiment of the invention, this light engine can provide powerful,pure, stable, inexpensive light across the Ultraviolet-visible-nearinfrared (UV-Vis-NIR). Light engines are designed to directly replacethe entire configuration of light management components with a single,simple unit. Power, spectral breadth and purity, stability andreliability data will demonstrate the advantages of these light enginesfor today's bioanalytical needs. Performance and cost analyses can becompared to traditional optical subsystems based on lamps, lasers andLEDs with respect to their suitability as sources for biomedicalapplications, implementation for development/evaluation of novelmeasurement tools and overall superior reliability. Using such sourcesthe demand for portable, hand-held analyzers and disposable devices withhighly integrated light sources can be fulfilled.

Lamp

In various embodiments of the present invention, a lamp emitswavelengths of light, which excite fluorescence from photosensitivetargets in the sample of interest. In various embodiments of the presentinvention, a lamp can be in the form of a tube, rod, or fiber of varyingor constant diameter. In various embodiments of the present invention, aconstituent light pipe can be made of glass, plastic, single or multipleinorganic crystal(s), or a confined liquid. In various embodiments ofthe present invention, a pipe either contains or is coated with a layeror layers containing, a narrowband luminescent material such as organicor inorganic compounds involving rare earths, transition metals ordonor-acceptor pairs. In various embodiments of the present invention, alamp emits confined luminescence when excited by IR, UV, or visiblelight from an LED, Laser, fluorescent tube, arc lamp, incandescent lampor other light source. In an embodiment of the present invention, a lampoperates through the process of spontaneous emission, which results in amuch larger selection of available wavelengths than is available forefficient stimulated emission (laser action).

Relay Optics

In an embodiment of the present invention, relay optics consist of lightpipes, optical fibers, lenses and filters, which optically transport thelight from a lamp to one or more capillaries and light pipes, opticalfibers, lenses and filters which collect and transport any generatedfluorescence to an appropriate detector or array of detectors, inconjunction with adaptors for coupling the excitation light into thecapillaries, coupling the emission light out of the capillaries and forenhancing physical discrimination of the excitation and emission. In anembodiment of the present invention, relay optics, including fibers, canbe constructed in a loop or as a cavity so that light from a lamp canpass through one or more capillaries multiple times to enhanceexcitation efficiency.

In an embodiment of the present invention, a number of lamps eachemitting one or more color of light can have their constituent lightpipes coupled in parallel or in series acting to produce multiple colorssimultaneously or in sequence. In an embodiment of the presentinvention, one or more lamps can illuminate single channels, multipleparallel channels, multiple channels in multiple dimensions, numerousspots along the analysis channel and/or reservoirs connected to the flowstreams.

In an embodiment of the present invention, lamps can be illuminatedcontinuously during the measurement process or can be pulsed on and offrapidly to enable time-based detection methods. In an embodiment of thepresent invention, a lamp can be switched off between measurements, toeliminate the heat output. This can be contrasted with alternatives suchas arc lamps or lasers that are unstable unless they are operatedcontinuously.

Illumination and Collection System

In an embodiment of the present invention, a flexible illumination andcollection system for capillary/fluorescence apparatus allows for avarying number of samples to be analyzed simultaneously.‘Simultaneously’ is herein defined as occurring close in time. Two lightpipes can irradiate two capillaries at the same time and thefluorescence from the molecules in one of the capillaries can be delayeddue to physical or chemical effects relating to absorption,phosphorescence and/or fluorescence resulting in a delay in thefluorescence from the molecules in one of the capillaries. Thisexcitation is still considered to result in ‘simultaneous detection’. Inan embodiment of the present invention, an illumination and collectionsystem can be adjusted for uniform illumination of multiple capillaries.In an embodiment of the present invention, illumination systems canirradiate an array of channels in an array of capillaries. In anembodiment of the present invention, an array of channels can be etched,molded, embossed into the capillaries. In an embodiment of the presentinvention, a set of wells intimately connected to fluidic conduits canbe stepped along the length of the fluidic conduit such that they can beinterrogated at numerous sites for the purposes of creating a map orimage of the reacting species.

In an embodiment of the present invention, an illumination andcollection system can emit multiple colors as desired. In an embodimentof the present invention, an illumination and collection system can bepulsed on and off as desired to reduce heat generation. In an embodimentof the present invention, an illumination and collection system can bepulsed on and off to allow time-based fluorescence detection.

In an embodiment of the present invention, illumination systems canirradiate homogeneous reactions within fluidic conduits or reservoirs.In an embodiment of the present invention, illumination systems canirradiate heterogeneous reactions on the surface of fluidic conduits orreservoirs. In an embodiment of the present invention, illuminationsystems can irradiate homogeneous or heterogeneous reactions on thesurface of or within the pores of a porous reaction support.

Other objects and advantages of the present invention will becomeapparent to those skilled in the art from the following description ofthe various embodiments, when read in light of the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES

Various embodiments of the present invention can be described in detailbased on the following figures, wherein:

FIG. 1 shows a schematic of a light engine subsystem consisting of alamp module and delivery optics;

FIG. 2 shows light engine output relative to a typical metal halide lampand 75 W xenon bulb;

FIG. 3 shows light pipe engine with <10 ns rise and fall times for fastswitching between bands;

FIG. 4 shows light engine stability over 24 hours of use;

FIG. 5 shows an eight color light engine layout, including a light pipeand five other solid state light sources, with dichroic mirrors tocreate a single coaxial 8-color beam. Each individual light source iscollimated so as to be efficiently combined and after color combination,the beam is refocused into a light guide for transport to the device orsystem to be illuminated according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIG. 1, is the light pipe engine 100 of an embodiment of theinvention. An individual lamp module driven by light pipe technologyconsists of an excitation source 102, typically one or more LEDs, and alight pipe 104. In an embodiment, the excitation source 102 and lightpipe 104 can be housed in a cylindrical waveguide 106. The excitationsource 102 drives luminescence in the light pipe 104, which is composedof a glass or polymer fiber. In an embodiment, light pipe 104 includes amirror 108. Glass fibers are either doped with a rare earth metal oractivated with a transition metal. Polymer fibers are doped with a dye.The fibers have fast response and decay times and can achieve a highefficiency through the design of delivery optics. The design andselection of the fiber determines the peak wavelength of the outputillumination; options exist to span the UV-Vis-NIR spectrum. Thebandwidth of the luminescence is narrow and can be further defined withthe use of band pass filters 110 integrated into the delivery optics. Inan embodiment, the delivery optics may include a band pass filter 110connected to a coupler 112, which can be attached to an optical deliverypipe 114 which leads to an instrument (e.g., a microtiter plate) 116.Output intensity is determined through the design of the pipe'sexcitation source.

The light pipe geometry provides a unique opportunity to shape anddirect the angular and spatial range of outputs. Combined with a highoutput power, the delivery optics can be readily tailored to couple thelight with various instruments and analyzers. Sensors, optical probes,microscope objectives or through liquid light guides, two-dimensionaloligomer and micro fluidic chips, and micro titer plates are allillumination fields that light pipe engines can readily support.Moreover, high output power enables illumination of large areas within achip, micro array or micro titer plate and, as a result, supporthigh-speed throughput in instruments where to date only scanning modesof operation could be envisioned.

The preferred mode of light pipe excitation is the application of one ormore LED's. This approach takes advantages of the benefits of LEDillumination: low cost, durability, and, at an appropriate excitationwavelength, high output power to drive the light pipe. In so doing theLED's shortcomings are managed. The lack of spectral stability and thehigh angular output characteristic of LED's do not impact theluminescence of the light pipe. Instead, the innovation of the lightpipe enables circumvention of the principle of etendue conservation. Alllight sources must conform to this dictate, which requires the spread oflight from a source never exceed the product of the area and the solidangle. Etendue cannot decrease in any given optical system.

The ability to modulate solid-state source outputs provides a uniqueopportunity for multiplexed fluorescent assays. Current light enginedesigns employ solid state materials with fast luminescence(approximately 10 ns.) The light pipe and LED have similar modulationcapabilities thus multiple light pipes tuned to different outputwavelengths can be employed to selectively detect multiple fluorescenttags within a given analysis. In addition, pulse modulation and phasemodulation techniques enable fluorescence lifetime detection and affordimproved signal to noise ratios. Each of the solid state units is trulyoff when it is off so low background signals and high contrast ratiosare possible.

Table III shows an embodiment of the present light pipe engineinvention's product and performance features. As improvements are madeto LED's and the cost of semiconductor lasers continue to decline, thetool chest of options available to light pipe engines will continue toevolve. The desired light engine can ultimately be powered by acombination of light pipe, LED's and lasers. The knowledge andcompetency to integrate any of these lighting technologies into thedelivery optics supports the requirements of each specific applicationand provides technical and commercial value.

TABLE III The light pipe engine feature set. Wavelengths UV - Vis - NIRColors Up to eight Intensity 1-10 W/cm² Bandwidths Adjustable SizeCompact Ease of Use Yes Modulation Up to 5 kHz Color control IndependentSystem Control Manual or computer Heat output Minimal Life time Long

Eight Light Engine Subsystem

FIG. 5 shows a schematic for a eight color light engine layout. In anembodiment of the invention, a eight color light engine 500 includes aluminescent rod 502 and five other solid state light sources 504, withdichroic mirrors 506 to create a single coaxial 8-color beam 508 (forexample selected from UV 395, Blue 440, Cyan 485, Teal 515, Green 550 or575, Orange 630 and Red 650 nm) leading to an output 510. Output 510couples beam 508 from light engine 500 to a liquid light guide (LLG),optical fiber, kohler etc. In this embodiment, a manual orelectromechanical filter slider 512 allows green yellow filtering of YAGgenerating 550 or 575 nm light. Additional colors can be used. Forexample, a color band centered at 550 nm can be replaced with a colorband centered at 560 nm. Each individual light source is collimated soas to be efficiently combined and after color combination, the beam isrefocused into a light guide for transport to the device or system to beilluminated according to an embodiment of the invention. In embodiments,solid state light sources 504 include: blue LEDs and UV LEDs combined inmodule 504 a; red and orange LEDs combined in module 504 b; teal LEDs inmodule 504 c, and cyan LEDs in module 504 d. In embodiments luminescentrod 502 generates green light. In an optional embodiment, a laser diode520 emitting 375 nm or 395 nm laser light is coupled to module 504 a. Inan optional embodiment, laser diodes 522 emitting 630 nm and 650 nmlaser light are coupled to module 504 b.

The light engine subsystem is designed to interface to the array ofbioanalytical tools with the expectation that the end user can take forgranted the high quality of the illumination. Table IV summarizes fourbioanalytical applications for which light engines including light pipescould replace more traditional illumination subsystems and offerperformance and cost advantages. For example, Kohler illumination intransmitted light microscopy requires that the light be focused andcollimated down the entire optical path of the microscope to provideoptimal specimen illumination. Even light intensity across a fairlylarge plane is a critical requirement. For stereomicroscopy, lighting isachieved with ring-lights at the objective and fiber optic lightspointed at the specimen from the side. In both cases, the light enginemust efficiently couple to a fiber optic cable.

TABLE IV Performance and cost analysis of the light pipe engine vs.traditional illumination subsystems in four key bioanalyticalapplications Fluorescence specification Sanger Sequencing Q-PCR FlowCytometry Microscopy Light engine Light Ar Ion Light Metal Light LasersLight Metal Pipe Laser Pipe Halide Pipe Pipe Halide Intensity 150-250150-250 0.5-1 0.2-1, 150-250 150-250    <50 1-50, W/cm² very λ very λspecific specific Wavelength 505 nm multiline 4 colors >2 colors 4colors Bandwidth,  10-30     26  10-30     15  10-30    <5 10-30    15nm Stability      0.1%    >1%      0.1%    >1%      0.1%    >1%     0.1%    >1% Switching,    <0.03 1-10,    <0.03 40, ext.    <0.031-10,    <0.03 40, ext. ms ext. shutter ext. shutter shutter shutterMTBF, hrs >10,000 <4,000 >10,000 <1,000 >10,000 <4,000 >10,000 <1,500Price    <$3K   >$5K    <$7.5K   >$10K    <$5K   >$5K    <$7.5K   >$10K

For portable diagnostic tools, the delivery optics must provide evenillumination over a small volume. These requirements are similar to, butless restrictive than those presented by capillary electrophoresis.Capillary electrophoresis requires an intense (10 mW) light focused ontothe side of a capillary tube with characteristic dimensions on the orderof a 350 pm outer diameter and a 50 pro inner diameter. To achieve thisgoal, the delivery optics were comprised of a ball lens to collect andcollimate light from the lamp module (already coupled into an opticalfiber), a bandpass filter to provide a narrowbandwidth of illumination,and an aspheric lens to focus the light at the center of the capillarybore. This approach yielded an 80 pin spot size and the desired 10 mW ofdelivered power to the capillary tube.

The design of delivery optics for microfluidic immunoassays requiresboth the even illumination required for optical microscopy and the smallvolume illumination required for capillary electrophoresis. Lightengines capable of delivering even illumination at the active sites in amicrofluidic array for detection of fluorescent tagged biomarkers havebeen designed for immunochemical as well as genomic applications. Theadvantages of the luminescent light pipe are providing commercial,readily available light engine solutions for illumination-detectionplatforms optimized for portable diagnostic tools.

Spectral Bands and Output Power

In various embodiments of the present invention, the light pipe engineperforms well compared with the output power across the visible spectrumto other lamps (see FIG. 2). Such comparisons beg for disclaimers as theoutputs of the commonly employed lamps change in time and degrade withusage. The light pipe engine is all solid state so they it issignificantly more stable and reproducible. FIG. 2 was taken within themanufacturers' specified lifetime for each lamp, by an independent userwell trained in biophotonics, these outputs represent typicalperformances of a common metal halide bulb, 75 W xenon bulb and that ofthe light pipe engine.

Such output comparisons are further complicated by mismatches betweenthe spikes of the metal halide bulb and light pipe light engine outputbands, However, noting such disparities it is fair to claim the outputsof the light engine across the visible spectrum compare well against theoutputs of a metal halide bulb in spectral windows that match theexcitation energies of some of the most commonly used fluors forbiotech: around 390 nm where DAPI and Hoescht can be excited; in thewindow most commonly associated with a cyan line of an argon ion laserand often used to excite Alexa dyes, green fluorescent proteins andfluoresceins; and in the red where neither of the lamps providesappreciable power for the likes of Cy5. The light engine also bests theXenon lamp across the palate of excitation wavelengths most common tobiotech: the Xenon lamp underperforms particularly in the violet, cyan,blue and red regions of the visible spectrum. Of course, more powerfulXenon lamps are often employed to provide enhanced performance at asignificant maintenance cost.

In another embodiment of the present invention, as seen in FIG. 2, theoutput of the green and amber bands have essentially doubled, such thaton a photon per photon basis the area under the curve for the arc lampvs. light engine are the same. Certainly the peak shapes, and figures ofmerit (height, FWHM, etc.) differ. However, no compromise in outputpower, even for the 546 nm band of the arc lamp, should be incurred as aconsequence of using a light pipe engine replacement.

Alternatively, a light pipe engine can be employed in a short duty cyclemode for power starved applications. When feasible, pulse widths of lessthan 100 ms at 10% duty cycles can actually improve the power output perband by a factor of 1.5 to 2.0 over longer duty cycles or in continuousmode of operation. Applications that employ multiple lasers andacousto-optic tunable filters (AOTFs) but need safe, cost effective andeasy to employ lighting solutions might benefit from such light engineperformance. Fluorescence microscopy for multicolor detection could takeadvantage of this option, for example. As could numerous otherbioanalytical platforms such as a light engine replacement for theoptical excitation from AOTF-based multicolor fluorescence detection forshort tandem repeat (STR) analysis in a micro-electrophoretic device, aglass microchip.

Fast Switching

Because of the solid state nature and independently operable designs ofthe lamp modules, coupled to fast (approximately 10 ns) decay times oftypical materials employed, a light pipe based light engine outperformsany broad spectrum source in terms of support for fast analyses. Lampbased sources are coupled to filters and/or shutters with mechanicalsupports that relegate them 1 to 50 millisecond regimes. Even LED basedlamps require filtering for most quantitative fluorescence basedanalyses. The light pipe based light engine incorporates all thatfiltering into its highly integrated design. Therefore switching timesare limited today by the electronics of the boards controlling thesources. Rise times of less than 20 μs and fall times of less than 2 usare typical (see FIG. 3). Moreover each color can be switchedindependently and is compatible with triggering by TTL, RS232 and USBand intensity control by RS232, USB or manually. This supportsexperiments where simultaneous excitation of multiple tags couldpreviously only be done with multipass excitation filters and broadbandsources. Using a light pipe engine, effectively instantaneous excitationof individual reporters can be manipulated within microsecond timeframes to achieve rapid, serial exposure of a biologic event to thevarious excitation bands with no external hardware beyond the lightengine itself.

Stability

Because a light pipe based light engine is based on solid statetechnologies, they are extremely stable both in short durationexperiments and over long term use. FIG. 4 depicts this stability. Lightengines are powered by 24 V power supplies operated in DC mode,therefore there is no 60 Hz noise. All colors perform similarly. In 24hours of continuous operation, the output fluctuates on the order of 1%.Short term stability on the order of 1.0 ms is approximately 0.5%. Shortterm stability for 0.1 ms is diminished by a factor of ten to 0.05%.

The foregoing description of the various embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many modifications andvariations will be apparent to the practitioner skilled in the art.Embodiments were chosen and described in order to best describe theprinciples of the invention and its practical application, therebyenabling others skilled in the art to understand the invention, thevarious embodiments and with various modifications that are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

Other features, aspects and objects of the invention can be obtainedfrom a review of the figures and the claims. It is to be understood thatother embodiments of the invention can be developed and fall within thespirit and scope of the invention and claims

What is claimed is:
 1. A method for analyzing a sample comprising: (a)providing excitation light from one or more photo luminescent lightsource together with excitation light from one or more light emittingdiodes to produce a beam of excitation light having one or more colors;(b) directing the beam of excitation light onto the sample; and (c)directing fluorescence from the sample onto one or more fluorescencedetectors.
 2. The method of claim 1, wherein the providing step producesthe beam of excitation light comprising a single coaxial beam.
 3. Themethod of claim 1, wherein the providing step produces the beam ofexcitation light comprising five or more selected wavelengths ofexcitation light.
 4. The method of claim 1, wherein the providing stepincludes the luminescent light source being a light pipe.
 5. Asolid-state light engine for adapted to analyze a sample having one ormore fluorescent tags comprising: at least one luminescent light source;at least one solid state light source; one or more dichroic mirrors; andwherein the at least one light luminescent light source, the at leastone excitation source, and the one or more dichroic mirrors are used toproduce a beam of excitation light having a plurality of colors, whereinthe beam of excitation light is adapted to selectively detect the one ormore fluorescent tags within the sample.
 6. The solid-state light engineof claim 5, wherein the one or more excitation sources arelight-emitting diodes (LEDs).
 7. The solid-state light engine of claim5, wherein the luminescent light source is a light pipe.
 8. Thesolid-state light engine of claim 7, wherein the luminescent lightsource is a single coaxial beam.
 9. The solid-state light engine ofclaim 5, wherein a plurality of luminescent light sources and aplurality of excitation sources have similar modulation capabilities,whereby the plurality of luminescent light sources are tuned todifferent output wavelengths and adapted to selectively detect multiplefluorescent tags within the sample.
 10. The solid-state light engine ofclaim 5, wherein each of the at least one solid state light sources arecollimated so as to be efficiently combined.
 11. The solid-state lightengine of claim 5, further comprising one or more filter sliders tofilter light from one or more of the at least one solid state lightsource.
 12. The solid-state light engine of claim 5, wherein the atleast one luminescent light source comprises one of a glass fiber dopedwith a rare earth metal, a glass fiber activated with a transitionmetal, and a polymer fiber doped with a dye.
 13. The solid-state lightengine of claim 5, wherein the light engine operates through a processof spontaneous emission.
 14. The solid-state light engine of claim 5,wherein the light engine comprises relay optics having one or moreoptical fibers.
 15. The solid-state light engine of claim 14, whereinthe relay optics are constructed in a loop so that light can passthrough one or more capillaries multiple times to enhance excitationefficiency.
 16. The solid-state light engine of claim 7, comprising aplurality of luminescent light sources, wherein the plurality ofluminescent light sources are coupled in parallel.
 17. The solid-statelight engine of claim 7, comprising a plurality of luminescent lightsources, wherein the plurality of luminescent light sources are coupledin series.
 18. A solid-state light engine comprising: at least oneluminescent light luminescent light source; at least one solid statelight source; one or more dichroic mirrors; and wherein the at least oneluminescent light source, the at least one excitation source, and theone or more dichroic mirrors are used to produce a beam of excitationlight having a plurality of colors.